Wind turbine designs and standards have been developed with today’s major markets in mind, Europe and North America. However, the bulk of future markets are expected to be in geographic areas where the meteorological and environmental conditions are much more extreme. Think cyclones, heavy rain and lightning. IRENA estimates that Asia will lead in onshore wind installations with over half of the total global capacity installed (>2,600 GW) by 2050. IRENA’s Alessandra Salgado, Michael Taylor and Francisco Boshell explain how new standards, testing, certification and maintenance processes are being created to cope with the new conditions. There is a need for customised hub heights and rotor sizes, reinforced towers and foundations, advanced wind turbine control and backup systems, better weather forecasting and a review of insurance policies. On top of that the farm operators, manufacturers and grid operators must agree on new operation procedures, suited to meet their specific weather conditions.
Wind technology deployment has spread in almost 140 countries due to the rich resource potential, cost declines and performance improvements that make wind power a competitive source of electricity. At the end of 2018 wind power accounted for around 23% -550 GW- of the global cumulative renewable energy installed capacity, with more than 50 GW added in 2018 only. This mature and competitive technology is expected to play a major role in decarbonising the energy sector, with analysis from the International Renewable Energy Agency (IRENA) highlighting that wind power deployment could grow to over 6,000 GW of installed capacity by the year 2050 in a scenario where the world meets its Paris Agreement goals.
Historically, wind turbine designs and technical standards have been developed reflecting the experience of the pioneer markets; i.e. in Europe and North America. However, in recent years deployment and the bulk of future markets are expected to be in geographic areas that don’t necessarily face the same meteorological and environmental conditions. IRENA estimates that Asia will lead in global onshore wind power installations with more than half of the total global capacity installed (>2,600 GW) by 2050.
This makes it important to verify that design standards, testing and certification processes are appropriate for the variety of meteorological and environmental conditions that wind projects will encounter in new and increasingly important markets outside Europe and North America. For a healthy and rapid growth market it’s crucial to ensuring that wind power technologies, wind frame design, and operations and maintenance (O&M) practices ensure that different weather conditions don’t adversely affect the performance and durability of the technology.
Wind farms in cyclone zones
As an example, with a shift in deployment into Asia and Latin America, in particular, wind farms are increasingly being exposed to tropical cyclones, which are among the world’s most intense and destructive storm types. They form over the tropical oceans, including the tropical North Pacific and South Pacific Ocean, the tropical North Atlantic and the Caribbean Sea. Under tropical cyclone conditions, wind turbines are exposed to a combination of risks triggered by the combination of high-speed wind, rainfall, lightning and, potentially, hail.
An added complication is that climate change may result in increased frequency of such destructive weather conditions and is almost certainly even today contributing to their greater intensity. In 2018 the tropical cyclone numbers were above average in all four Northern Hemisphere basins, with 70 cyclones reported by 20 November of that year, compared to the long-term average of 53 cyclones per year (WMO, 2018).
Extreme wind speeds, lightning, heavy rain
Tropical cyclones with extreme wind speed might cause structural or superficial damage to wind turbines and potentially have a significant impact on the wind turbines and wind farm output. These storms also bring associated risk of lightning strikes that can damage blades by direct strike if the necessary measures aren’t taken, but also connected devices due to indirect strikes. Heavy rains can cause surface flooding or erosion that may affect foundations, while they can also affect the access to the wind farm and the electrical infrastructure necessary for export of electricity. An example that suffered all these meteorological factors, was a wind farm in China, struck by a category 4 typhoon known as “Usagi”. The wind farm incurred $16m in damage costs: these losses included damage to different turbine components, including yaw systems, sensors, rotor blades, a tubular tower collapse and a wind turbine fire.
Until very recently, tropical cyclones were excluded from the design requirements for wind turbine manufacturers in international standards, as they were not generally applicable to Europe or the parts of North America where wind farms were deployed. The risk assessment and mitigation strategies therefore had to fall on the owner and other stakeholders of the wind farm, and although industry best practices can be applied – during the development, design and operational phase, including insurance – these stakeholders may not have had the necessary experience to fully address the range of risks.
New design standards
But the new version of the international standard (edition 3 of IEC 61400-1) includes a special class to account for wind farms located in sites influenced by tropical cyclones that have been developed based on standards that already accounted for this (such as the Japanese one). This represents an example of standards being adapted to take into account the changing risks facing newly developed wind farms in such locations.
IRENA analysis has shown that industry best practices and standards can be applied to mitigate the risks from tropical cyclones. Project developers and investors need to implement preventive mitigation measures, which appear to have limited financial implications. Some of the main strategies to be considered are:
i) inclusion of international and locals standards in the design phase
ii) consider customised hub height and rotor size to better withstand extreme wind speeds in the turbine design, reinforced wind turbines components such as towers and foundations, advanced wind turbine control and backup systems
iii) establish agreed operation procedures to follow between the farm operator, manufacturers and grid operator in the instance of a tropical cyclone, increase maintenance on the control and backup systems, enhanced and specific weather forecasts.
Figure 1 gives a more comprehensive view of applicable mitigation strategies that should be considered when developing or adapting a wind farm to tropical cyclone conditions.
Wind turbines manufacturers do not typically warrant damages under tropical cyclones, so these need to be covered through the wind farm insurance. It is therefore important that wind farm owners are explicit about what the scope of the coverage of their insurance is and whether it will cover, beyond the physical damage to components, the economic impact due to downtime and/or repairing affected components.
Wind power is a mature and highly-reliable technology, capable to withstand severe weather conditions. However, as deployment is increasingly concentrated in areas with harsh weather, it is important that technology and related technical standards continue to evolve to document and implement lessons learnt and best practices to assure that the benefits of low-cost electricity from this technology are reaped by end-consumers.
IRENA is working on a forthcoming report, studying the impact of extreme weather events and harsh operating environments in wind and solar PV technologies. The report will include an analysis of different weather events and harsh operating conditions, assessing associated costs and whether the existing quality assurance frameworks are adequate, providing key recommendations for the main players in the growing wind markets of today.
- IRENA (forthcoming) impact of extreme weather events and harsh operating environments in wind and solar PV technologies
- IRENA (2018) Nurturing Offshore Wind Markets: Good practices for international standardisation: https://www.irena.org/publications/2018/May/Nurturing-offshore-wind-markets
- IRENA (2019) Global energy transformation: A roadmap to 2050 (2019 edition) https://irena.org/publications/2019/Apr/Global-energy-transformation-A-roadmap-to-2050-2019Edition
- World Meteorological Organization 2018 WMO climate statement: past 4 years warmest on record https://public.wmo.int/en/media/press-release/wmo-climate-statement-past-4-years-warmest-record
- Flaticon https://www.flaticon.com/